Transcript Primordial Matter in the Solar System

Primordial Matter in the Solar System
• Solar system formed out of cold, dense
hydrogen gas cloud, but containing ALL other
heavy elements
• Sun too young to have synthesized any other
elements, still in the H  He production stage
(about half-way)
Planetesimals or Minor Planets
• In addition to the Sun and 8 planets and
we have
-- Asteroid Belt, rocky/metallic bodies (also called minor
planets or planetesimals ) up to 1000 Kms in diameter,
-- Planet never formed, or broken up by Jupiter’s tidal
effect
-- Pluto and Kuiper Belt Objects (KBOs)
‘Debris’ of the Solar System
• The ice/rock dichotomy is most starkly evident in
comets and asteroids
• Meteoroids in space; meteors or meteorites when
they enter the Earth’s atmosphere
 Comets/Meteors are mainly ice(snow) balls,
and
 Asteroid/Meteorites are rocky/metallic objects
• Comets would have been a source of water on the
Earth
• Comets originate in either (i) the Oort Cloud at the
edge of the solar system, or (ii) the Kuiper Belt
beyond the orbit of Pluto
Planetesimals etc.
• Minor planets or asteroids, comets, and
other objects orbiting the Sun obey
Kepler’s laws
• Kuiper Belt Objects (KBO’s) are
planetesimals beyond Pluto’s orbit
• Recently discovered (at least) two
“planets” comparable to Pluto, named
Xena and Sedna
Asteroids
• Over 5000 found between 2.8-3.2 AU
• Keplerian orbits, e.g. P2 = a3
• Gaps, such as the Kirkwood Gap, due to orbital
resonance with Jupiter and other asteroids (like
the Cassini Division in Saturn’s rings)
• Jupiter maintains the asteroid belt, although
may have prevented planet formation
• Families of asteroids: Floras, Trojans, and
the AAA objects -- Amors Appolos, Atems –
that could come close to Earth (Dinosaurs !)
Asteroids (Contd.)
• Small albedo ~ 0.1-0.2
• Masses: Largest about 1/20,000 of the
mass of the Earth; all asteroids combined
would still be only about 1/1000 of M(E)
• Composition of Asteroids  Meteorites;
metallic and silicates mixed with organic
carbon compounds
Meteorites
• “Stones from Heaven”  Excalibur, Ka’aba
(black) stone, etc.; survive atmospheric friction
and land on Earth)
• Metallic ones with pure iron; surprising ?
• Extraterrestrial origin since Iron never occurs
in pure form on the Earth but as iron ore
compounds
• Stones (silicates), Irons (iron and nickel),
Stony-irons (silicates and metals)
• Largest meteorite (Namibia): 7m3 , 60 tons
• Ages from radioactivity  4.6 Gyrs
Typical asteroids
Meteorite damage!
Barringer Crater (Flagstaff, AZ)
Stony Carbonaceous chondrites
(Allende Meteorite)
Stony Iron Meteorite
Glassy nodules
on exterior. Why?
Iron Meteorite
(Interlocking crystal pattern)
Comets
Comets: Head and Tail
Where is the Sun (which direction) ?
Orbits of comets
Altering orbits of comets
Long-period
comet
Short-period
comet
The Tale of Two Tails!
Gaseous and Ionic Tails
ice/dust tail (white)
Ion tail (blue)
Ice/dust tail: Evaporating
mattter as the comet
approaches the Sun
Ion tail: charged particles
Electrons, protons, ions
pushed directly away by
charged particles in the
Solar Wind
Structure of comets
The vaporizing nucleus
Cometary Orbit Around the Sun
Comets
• Ancient remnants of the Solar nebula
• Long period comets from the Oort Cloud; short
period ones from the Kuiper Belt
• Total number about 10 trillion !
• Structure  Nucleus, Coma, H-cloud, Tail
• Tail(s): Gaseous and Ionic
• Nucleus  ~ 5-10 Kms diameter, less than ten
billionth of the mass of the Earth
• Total mass in comets about 1000 times
Earth’s mass (all the planets combined)
Comets (Contd.)
• Formed out of the building blocks of the
Solar System: Ices (H2O, CO2), like the outer
planets
• Large eccentricity
• Evaporate while approaching the Sun; the
tail gets longer
• Sometimes break up, e.g. Comet
Shoemaker-Levy in 1993
• Meteor Showers, e.g. Leonid shower in 2001
Meteors
• “Shooting Stars”
• Icy/Dusty pieces like cometary material, or
small pieces from comets
• Burn up completely in the atmosphere
• Meteor showers appear to originate at a
common point  optical illusion like
parallel rail tracks meeting in the distance